High temperature water resistant lubricating greases



United States Patent M HIGH TEMPERATURE WATER RESISTANT LUBRICATIN G GREASES James C. MacKenzie, Wellesley Hills, Mass, assignor to Godfrey L. Cabot, Inc, Boston, Mass, a corporation of Massachusetts No Drawing. Application May 4, 1956 Serial No. 582,668

6 Claims. (Cl. 252-28) This invention relates to a new and improved grease composition of the type in which an organic lubricating oil is thickened to a grease consistency by means of a finely-divided inorganic solid material. More particularly it is concerned with grease compositions of said type characterized by outstanding resistance to water even at elevated temperatures.

Although conventional bodied lubricants containing inorganic thickening agents are able to maintain grease consistency at temperatures at which soap-thickened greases melt and become unserviceable, they are normally even less resistant to moisture than the soap greases. Many efforts have been directed in recent years to the problem of producing less water-sensitive greases made with the inorganic type thickeners. The addition of various hydrophobic organic materials to either the inorganic thickener or to the grease itself has been suggested for this purpose by previous workers. Although many of these prior art additives did provide some improvement in the water-resistance of such greases at ordinary temperatures, almost all of them were relatively ineifective at elevated temperatures. For example, the ability of such a modified grease to remain unaffected after being subjected to boiling water for 1 hour was considered a remarkably good performance prior to the present invention.

Because of the prevalence of moisture and since the primary advantages of greases made with inorganic thickening agents can only be realized at elevated temperatures, the achievement of full high temperature water resistance is imperative if such greases are to attain widespread usage. The cost of providing this high temperature water stability is also an important consideration especially since it has been found that additives used for this purpose tend to reduce the thickening efficiency of the inorganic bodying agent and thus add to the total cost indirectly as well as directly.

The principal object of this inventionis to provide grease compositions which not only retain grease characteristics over a relatively, Wide range of temperature but remain serviceable after extended usage at elevated temperatures even in the presence of moisture.

Another object is to provide inorganic thickening agents which, though they are normally relatively hydrophilic, have been modified to the point where they possess outstanding surface characteristics that render them decidedly superior for many applications to previously available'surface-treated inorganic materials.

It is also an object of this invention to provide additives having outstanding capacity for imparting hydrophobicity to greases thickened with finely-divided inorganic materials but which do not reduce the bodyingpower of the said inorganic material as much as many of the less effective additives previously used in such greases.

Still another object is to provide grease compositions having outstandingly superior high temperature waterresistance without any outstanding increase in cost over the ordinary high temperature greases which are stable at high temperatures only under relatively dry conditions.

Patented Aug. 4, 1959 where R is a monovalent hydrocarbon radical containing at least 5 and preferably at least 8 carbon atoms linked consecutively to one another in an open chain and containing a total of at least 8 and preferably at least 12 carbon atoms; R is hydrogen or a monovalent hydrocarbon radical but preferably is hydrogen; n is an integer which is at least 2 but not over 4; and x is an integer from 1 to 3 but preferably is 1.

These compounds can be described simply as polyamines composed entirely of the three elements, C, H and N and containing a single primary amino group and l to 3 non-primary amino groups one of which is substituted by a hydrocarbon radical containing a medium to high molecular aliphatic chain. This hydrocarbon radical R, like R when the latter is not hydrogen, is preferably purely aliphatic but may also be either arylsubstituted aliphatic or aliphatic-substituted aryl and, in any case contains not over about 24 and preferably not over 20 carbon atoms.

Although polyamines are one of the general classes of hydrophobic cationic agents which have been broadly suggested as additives for imparting water-resistance to greases thickened with finely divided inorganic materials, the only true polyamines which have been specifically disclosed for this purpose are quite different from the particular class of polyamine to the use of which the present invention is directed. Thus, the only true polyamines mentioned in this connection at all are the simple polyalkylene polyamines such as diethylene triamine, triethylene tetramine, and tetraethylene pentamine, etc. However, these compounds proved to be almost totally ineffective for imparting water-resistance and, as indicated in US. Patent 2,554,222 by Stross for example, were not usually used per se but were first reacted with fatty acids. Although the derivatives resulting from this reaction were used by Stross and others to make greases that are water-resistant at room temperature, said derivatives are really amides and/or salts of the fatty acids in question and not polyamines at all. Moreover, such derivatives have been found to be decidedly inferior to the polyamines of the present invention for imparting high temperature water resistance to greases thickened with finely-divided inorganic materials.

The polyamines of interest in the present invention can be easily prepared, by reacting, for example, a medium to high molecular hydrocarbyl substituted primary or secondary amine with acrylonitrile and then catalytically hydrogenating the resultant amino nitrile in the following manner:

Starting with crude primary fatty amine derived from natural oils such as coconut oil, soya bean oil or tallow,

mixed polyamines suitable for use in the present invention can be made at very reasonable cost. In fact, such technical grade products in which R is hydrogen and R is from to 20 carbon atoms in size, are now available on the market, being sold for example by Armour Chemical' Division under the trade name of Duomeens." Fatty acid salts of said Duorneens are also available and can be used in place of the polyamines of this invention. However, such fatty acid salts are not the full equivalents of the corresponding polyamines because said salts are considerably less eifective, on a weight basis as well as on the basis of total cost, than the corresponding polyamines. Thus, much larger amounts are required to impart a given level of water-resistance to the resulting greases, and, moreover, the salts cause a much greater reduction in the thickening efficiency of the finelydivided inorganic bodying agent used.

The exceptional ability of. the above-defined class of polyamines to impart high temperature water resistance to grease compositions thickened with finely-divided inorganic materials appears to-be independent of the nature of the particular oleaginous liquid vehicle used in said composition. Thus, the same superior results are obtained regardless of whether the grease is based upon a conventional mineral lubricating oil, or upon synthetic oleaginous compositions having similar viscosities and lubricating characteristics, or upon mixtures of the two. Any synthetic oleaginous liquid which is substantially immiscible with water and which is sufiiciently stable to retain its oily character at elevated temperature is suitable. Some of the better known and most widely used of the synthetic lubricants are polyglycols and other polyalkylene oxide derivatives, silicone oils and high molecular weight aliphatic diesters, especially branched chain diesters of dicarboxylic acids such as adipic, azelaic, and sebacic.

Likewise, the exceptionally beneficial water-proofing effect of the polyamines of this invention is not limited to any particular inorganic thickening agent. Accordingly, the inorganic thickening agent used in the improved greases of this invention may be any non-abrasive inorganic colloid capable of producing a grease-like structure when intimately incorporated in an oleaginous liquid vehicle. Among the most useful and best known inorganic thickening agents are various polyvalent metal and metalloid oxides especially the so-called gel forming oxides such as those of aluminum, titanium, zirconium, silicon, magnesium, zinc, etc., and mixtures of said oxides particularly when they are in the expanded aerogel form in which they can, with care, be recovered after precipitation from either liquid or gaseous phase reactions. Naturally occurring inorganic colloids can also be used such as the various clays which expand and increase in volume in the presence of water and other liquids, especially for example certain bentonites, hectorites, and other montmorillonite clays as well as attapulgites and similar polygorskite clays.

Of course, the inorganic thickening agents which, because of their outstanding grease forming capacity and thickening power at relatively low concentrations, are preferred in the practice of this invention are the substantially anhydrous, extremely finely-divided metal and metalloid oxides which are formed pyrogenically by a high temperature reaction in which all reactants and all other products save said oxides are in the vapor state. Such products which have average particle sizes of less than 0.05 micron and may consist of silica, alumina, zirconia, titania or mixtures of these oxides, for example, can be produced by flame hydrolysis of volatile halides of the corresponding elements, suitable processes for such reactions having been disclosed, for example, by Stokes and Kistiakowsky in copending applicationSer. No. 129,089, filed January 23, 1949, and by Wagner in U. S. applications Ser. Nos. 344,840 and 455,369, filed March 26, 1953, and Sept. 10, 1954, respectively.

Although such pyrogenic oxides are presently somewhat more expensive per pound than some of the wetprocess oxides or naturally occurring inorganic thickening agents, the total cost of a water-resistant grease suitable for a given level of high temperature service is usually lower when the said pyrogenic materials are used. There are two important reasons for this. First, they are more efficient thickeners and secondly, apparently as a result of the lower concentrations in which they can be used, lesser amounts of the polyamine waterproofing additive appears to be necessary as well. In other words the amount of the polyamine additive required for a given job appears to depend mostly upon the total amount of inorganic thickening agent present. Thus, the polyamines of this invention should be used in amounts equivalent to at least about 5% by weight of the weight of the finely divided inorganic thickener in order to obtain a significant improvement in the waterresistance of the resultant grease at elevated temperatures, while 10 to 40% of the polyamines on the same basis represents the range for optimum results. Still larger amounts than 40% can, of course, be used without harm, but the additional benefit, if any, will seldom make the added cost seem warranted.

The concentration of the inorganic thickening agent in the finished grease, will in turn depend not only upon its characteristic thickening power but also upon such factors as the consistency desired in the finished grease and the viscosity and other characteristics of the unthickened oleaginous vehicle used therein. Considering the wide variety of inorganic colloids which can be used as the grease bodying agents and the wide variations that are possible in the oleaginous liquids used as grease vehicles, the concentration of inorganic thickener used in greases made for various purposes in accordance with this invention could cover quite a range, all the way from about 2 to about 20% by weight of the total grease composition, for example. However, in grease compositions of the consistency preferred for most uses, the inorganic thickener concentration will run from about 5 to about 15% by weight, except that for the preferred class of thickener, namely the very finely-divided, substantially anhydrous pyrogenic oxides of less than 0.05 micron in average particle size, the usable concentration will generally be from about 2 to about 14% by weight with the range from about 3 to about 12% being preferred.

The three absolutely essential ingredients of the grease compositions of this invention, namely (1) the substantially water-insoluble hydrocarbyl polyamines, (2) the organic lubricating oil, and (3) the inorganic thickening agent, have been described above together with a general guide to the relative proportions in which they can be combine. However, other ingredients not absolutely essential to the attainment of the objects of this invention, may be and often are included in grease compositions produced, in accordance with this invention, by combining the three above-mentioned essential ingredients. Such additional ingredients may include, for example, extreme pressure additives, oxidation inhibitors, viscosity index modifiers, corrosion inhibitors, coloring agents, or any other minor ingredients the presence of which does not interfere with the performance of the composition as a water-resistant grease in high temperature service. The expression consisting essentially of is used herein, including the appended claims, to indicate that only the absolutely essential ingredients of the grease composition are being named but that additional unnamed ingredients mayalso be present in such amounts as do not substantially interfere with the desirable properties and characteristics of the grease composition set forth.

The manufacture of the grease compositions of this invention can be carried out very easily, as any process suflices in which the several ingredients are intimately mbined and mixed together, For best results, the mixwa n.

ing action should include a considerable amount of internal shear. This shear can be produced, for example, by intensive mechanical working such as in roll milling, ball milling, or colloid milling or by high speed kinetic flow such as in pressure homogenization. One of the preferred techniques for making said grease compositions involves dissolving the polyamine additives in the oleaginous vehicle and subsequently incorporating the inorganic thickening agent by milling it into the compounded vehicle. It is also possible to disperse the polyamine additive on the inorganic thickening agent prior to its incorporation in the oleaginous vehicle. The resulting hydrophobic inorganic thickener can be used with advantage in elastomers, certain paint systems, etc. as well as in greases.

The use of elevated temperatures in combining and mixing together the various ingredients of the grease may simplify the manufacturing process in many instances. The high temperature water resistance of a given grease composition is not reduced by its having been heated during the manufacturing process to a temperature of 100 to 200 C., and it may even, in some cases, be better than that of a grease of the same composition prepared without heating.

The following specific examples illustrate the outstanding efiectiveness of the particular substantially water-insoluble hydrocarbyl polyamines of this invention in imparting hightemperature water-resistance to greases thickened with inorganic materials. These examples also demonstrate the superiority of said polyamines. for this application over any polyamines and/ or derivatives thereof previously suggested for such use. By virtue of their specificity, these examples will convey more clearly the relative thickening power and grease forming capacity of some of various possible inorganic thickening agents and will give thereby a better understanding of the relative proportions in which the essential ingredients of this invention can be used to make greases of various consistencies. However, it should be clearly understood that these examples are given for purposes of illustration only and not by way of limitation of the scope of the present invention.

Example I Twelve parts by weight of a pyrogenic silica made by high temperature hydrolysis of SiCL; vapors in a flame produced by burning a hydrogen-containing fuel (said silica analyzing about 99% SiO and having an average particle size of about 20 millimicrons) was intimately incorporated into 88 parts by weight of a refined paraffin base lubricating oil having a viscosity of 65 SSU at 210 F. and a viscosity index of 100 to give a grease of medium consistency. While the resulting grease exhibits good high temperature stability under dry conditions, it is so sensitive to water that it will disintegrate rapidly in contact with condensed water even at ordinary temperatures and will change consistency rapidly in contact with a moist atmosphere, especially at slightly elevated temperatures.

Five modified greases were then made up in a similar manner except that prior to incorporation of the pyrogenic silica there was dissolved in the oil about 2.6 parts by weight of one of the following amines Amine additives suggested by prior art.

A polyamine of this invention.

The resulting modified greases were pressed into cylindrical plugs about 1 cm. in diameter and 3.5 cm. in length. The water stability of said greases was then tested by observing the time required for such a plug of each grease to start to fragment in water at room temperature and in boiling water. The results are shown in the following table.

Maximum Time for Which Grease Retained Useful Consistency Grease (a) in Cold Water (b) in Boiling Water 2 weeks 1 hour. 1 to 2 days 1 hour. approx. 1 to 2 hours... approx. 1 minute. 2 weeks 1 hour. 2 weeks-.. hours.

By comparison, the most water resistant soap-thickened greases (based on lithium soaps) are no better than modified non-soap greases #1 and #4 above.

The outstanding superiority of the particular class of polyamine covered by the present invention in imparting water-resistance, particularly at elevated temperatures, is clearly demonstrated by the above results.

Pyrogenic alumina, titania, zirconia or mixtures of such oxides of equivalent particle size may be substituted for the pyrogenic silica in the above example, and/or synthetic lubricant oils can be substituted for the petroleum oil vehicle without significantly afiecting these results.

Example II Five parts of N-(tallow hydrocarbyl) propylene-1,3 diamine and 52 parts of pyrogenic silica of about 20 millimicrons in average particle size were milled into 750 parts of refined paraflin base lubricating oil having a viscosity at 210 F. of 148 SSU and a viscosity index of 102, using a 3-roll mill, to produce a grease having a worked penetration at 71 F. of 298 by ASTM method D-217-48. On being refluxed in boiling water, uncompressed lumps of said grease 'Were still intact and substantially unchanged in consistency after about 50 hours and still of useful consistency after over l00hours.

Substantially the same results can be obtained in the above example using an aerogel silica obtained by solvent displacement from a precipitate from a liquid phase reaction but the amounts of silica thickener and diamine additive must be increased by about 30%.

In place of the N-(tallow hydrocarbyl) propylene- 1,3 diamine in the above example equal amounts of N-(alkyl phenyl) propylene-1,3 diamine in which the alkyl group averages about 12 carbon atoms in size may be substituted with substantially the same results.

Example III About 22 parts of N-(coconut hydrocarbyl) propylene- 1,3 diamine were dissolved in about 750 parts of the refined lubricating oil used in Example I and parts of the pyrogenic silica of Example I were then stirred into the modified oil using a Hobart mixer. The resulting grease had a worked ASTM (60 strokes) penetration at 73 F. of about 296. An uncompressed lump of this grease remained intact and substantially unchanged in consistency and lubricating power after being subjected to boiling water for 98 hours.

If in place of the diamine of the above example there is substituted the dioleate salt of the diamine of Example I in equal amount, the resulting grease is undesirably thin having a worked ASTM (60 strokes) penetration of over 411 at 74 F. In order to obtain a grease of equal consistency and equivalent high temperature water resistance the loading of pyrogenic silica in the composition must be increased by over 30% and the dioleate salt must be used in amounts at least 50% greater than that of the diamine shown above.

Having described my invention and preferred embodiment thereof, what I claim and desire to secure by U.S. Letters Patent is:

1. A grease composition stable at high temperatures even in the presence of water consisting essentially of a lubricating oil, a finely-divided inorganic thickening agent chosen from the group consisting of metal oxides, metalloid oxides, bentonitic clays and attapulgite clays, the amount of said thickening agent being sufiicient to impart a grease-like consistency to the composition, and about to 40% by weight of said thickening agent of a polyamine having the formula where R is a monovalent hydrocarbon radical containing a total of from about 8 to about 24 carbon atoms at least 5 of which are consecutively linked to one another in an open chain, R is selected from the group consisting of hydrogen and monovalent hydrocarbon radicals containing from about 1 to about 24 carbon atoms, n is an integer from 2 to 4 and x is an integer from 1 to 3 the exact values of n and x being selected so that the product of n-x is not greater than 6.

2. A water-resistant thickened lubricant composition suitable for high-temperature use consisting essentially of a lubricating oil, an inorganic oxide thickening agent in an amount sufiicient to impart a grease-like consistency to the composition, and about 5% to 40% by weight of said inorganic thickening agent of a polyamine having the formula where R is a monovalent hydrocarbon radical containing a total of from about 8 to about 24 carbon atoms at least 5 of which are consecutively linked to one another in an open chain, R is selected from the group consisting of hydrogen and monovalent hydrocarbon radicals containing from about 1 to about 24 carbon atoms, n is an integer from 2 to 4 and x is an integer from 1 to 3.

3. A water-resistant high temperature grease composition consisting essentially of from about 2 to about 14% by weight of a substantially anhydrous pyrogenic silica the average particle size of which is less than 0.05micron, from about 10% to about by weight of said silica of an'aliphatic diamine having the formula where R is a monovalent aliphatic hydrocarbon radical containing from about 12 to about 20 carbon atoms and R is selected from the group consisting of H and monovalent aliphatic hydrocarbon radicals containing from about 1 to about 24 carbon atoms, and, accounting for substantially all of the remainder of said composition, a solvent-extracted mineral oil.

4. The composition of claim 3 in which R is hydrogen.

5. A hydrophobic filter and bodying agent consisting essentially of a colloidally subdivided inorganic solid selected from the group consisting of metal oxides, metalloid oxides, bentonitic clays and attapulgite clays and dispersed on the surface of said inorganic solid an aliphatic polyamine having the formula where R is a monovalent aliphatic hydrocarbon radical containing from about 8 to about 24 carbon-atoms, R is selected from the group consisting of hydrogen and monovalent aliphatic hydrocarbon radicals containing from about 1 to about 24 carbon atoms, n is aninteger from 2 to 4 and x is an integer from 1 to 3, the exact values of n and x being so chosen that the productVn-x is not greater than 6.

6. The composition of claim 5 in which R -is hydrogen.

References Cited in the file of this patent UNITED STATES PATENTS 2,623,852 Peterson Dec. 30, 1952 2,681,314 Skinner et al. June 15, 1954 2,748,081 Peterson et al May 29, 1956 OTHER REFERENCES Duomeens, Feb. 21, 1956, by Armour Chem. Div., 4 page booklet. 

1. A GREASE COMPOSITION STABLE AT HIGH TEMPERATURE EVEN IN THE PRESENCE OF WATER CONSISTING ESSENTIALLY OF A LUNRICATING OIL, A FINELY-DIVIDED INORGANIC THICKENING AGENT CHOSEN FROM THE GROUP CONSISTING OF MWTAL OXIDES, METALLOID OXIDES, BENTONITIC CLAYS AND ATTAPULGITE CLAYS, THE AMOUNT OF SAID THICKENING AGENT BEING SUFFICIENT TO IMPART A GREASE-LIKE CONSISTENCY TO THE COMPOSITION, AND ABOUT 5% TO 40% BY, WEIGHT OF SAID THICKENING AGENT OF A POLYAMINE HAVING THE FORMULA 